1. Field of the Invention
The invention relates to an internal combustion engine, comprising a cylinder block and a cylinder head, with at least one first cooling jacket being arranged in the cylinder block, and at least one second cooling jacket being arranged in the cylinder head and a cooling fluid can flow through the cooling jackets substantially in the longitudinal direction of the internal combustion engine, and with both the cylinder block as well as the cylinder head having separate inflows and outlets for the cooling fluid which communicate with the respective cooling jacket in the cylinder block and cylinder head. The invention further relates to a method for operating this internal combustion engine.
2. The Prior Art
It is known to cool the cylinder block and the cylinder head of an internal combustion engine by a cooling circuit which usually contains water which is guided to the radiator after passing through the engine in order to bring the cooling water there to a lower temperature. It is also known to arrange a pump in the cooling circuit. It has been noticed in internal combustion engines that the cylinder head needs to be cooled more strongly than the cylinder block which, as is known, is subjected to lower thermal loads. This is considered in the known cooling systems only in such a way that one forces a relatively large amount of cooling fluid through the cylinder head to the thermally critical regions in that the entire coolant quantity is allowed to flow from the cylinder block through geometrically limited passages through the cylinder head gasket, which inevitably leads to high pressure drops.
In the case of cooling chambers in the cylinder head with longitudinal flow which are connected with the cooling chambers of the cylinder block via passages, there is a disadvantage that the first cylinder is cooled worse than the cylinders which are arranged downstream in the cooling circuit of the cylinder head because the cooling jacket of the cylinder head acts as a collecting element and the accumulation of the coolant quantity leads to higher flow speeds with each cylinder and thus leads to better cooling effects on the one hand but also causes an increasing pressure difference along the cooling jacket on the other hand. This significant pressure difference along the engine requires a compensating, oppositely directed and clear gradation of the passages through the cylinder head gasket, leading inevitably to very small dimensions of the smallest gasket passages, which is why the total pressure drop typically can reach high unfavorable magnitudes in order to provide acceptable cooling conditions also for the first cylinder. Furthermore, flow through thermally critical regions which are substantially oriented transversally to the longitudinal direction of the engine, especially in the region of the exhaust valve seat, is adverse as a result of the inexistent pressure difference transversally to the engine, with the critical regions not being cooled optimally.
It is further known to use separate cooling circuits for cylinder block and cylinder head. A cooling system for an internal combustion engine is known for example from DE 196 28 542 A1, in which the cylinder head is cooled by a first cooling water circuit and the cylinder block by a second cooling water circuit, with the cylinder head and cylinder block being flowed through in parallel. An improved cooling of the cylinder head can thus be achieved. Internal combustion engines with divided cooling circuits are further also known from the publications JP 60 019 912 A2, JP 57 146 010 A2 or U.S. Pat. No. 4,370,950 A. Even in the case of internal combustion engines with divided cooling circuits, thermally critical regions which are substantially oriented transversally to the longitudinal direction of the engine show adverse flow as a result of the inexistent pressure difference and are thus not cooled optimally.
It is the object of the invention to avoid these disadvantages and to achieve an even and optimal cooling in combination with acceptable pressure drops and minimization of parallel flows in an internal combustion engine of the kind mentioned above.